The primary parts of a basic, desktop computer system include a keyboard, a monitor, and a box that contains most of the electronic devices that make the computer system work. The box includes a chassis or frame that houses the electronic devices in a convenient form factor. Included in the chassis are electronic devices externally apparent to the computer system user such as a disk drive, CD-ROM drive, and various switches, knobs, sockets, and light indicators. Removing the cover that protects these electronic devices reveals many more key electronic devices including, for example, processors, memory units, clocking devices, interfaces, and peripheral components, all of which are electrically coupled together on printed circuit boards (PCBs). One of these PCBs, usually the PCB containing the central processing unit and main memory, is referred to as the motherboard.
FIG. 1A is a top-down view of motherboard 11 inside chassis 15 in accordance with the prior art. Motherboard 11 is attached to the bottom of chassis 15 by screws 10, and is coupled to socket 12 of riser 13. The edge of motherboard 11 is contained within motherboard edge guide 14. FIG. 1B is a side view of the structure of FIG. 1A along the length of motherboard 11, showing how motherboard 11 is affixed to chassis 15 by screws 10, socket 12, and motherboard edge guide 14. Motherboard 11 contains electronic devices and interconnect lines (not shown), many of which are disposed on the top side of the motherboard.
Motherboard 11 includes electrical contact regions disposed at the edge of the motherboard in the region inserted into socket 12. Motherboard edge guide 14 serves to support the edge of motherboard 11 and to guide the motherboard into socket 12, aligning the electrical contact regions on the edge of the motherboard with corresponding electrical contact regions inside the socket. In this manner, the proper electrical couplings between motherboard 11 and socket 12 are made.
As consumers demand increased computer system functionality in smaller form factors, more electronic devices need to be squeezed into the limited space of PCBs, including motherboard 11. One drawback of the prior art system of FIG. 1A is that there is a significant area of "keep-out" regions on the motherboard. A keep-out region is a region on the PCB where electronic devices cannot be placed because of some mechanical obstruction. For example, screws 10 create keep-out regions in the vicinity of the screw heads, and motherboard edge guide 14 creates a keep-out region in the vicinity of the portion of the guide that overlaps motherboard 11.
As consumers demand lower priced computer systems, it becomes desirable to promote computer system chassis designs that can accommodate PCBs, such as motherboards, from any number of different motherboard vendors. Promoting motherboard competition in this manner typically has the effect of lowering motherboard prices. Motherboards from different vendors, however, may be different sizes. Unfortunately, because the chassis design of the prior art structure of FIG. 1A fixes the distance between motherboard edge guide 14 and the back of chassis 15, this chassis design is unable to accommodate motherboards of varying lengths.
As consumers and computer support personnel demand more easily serviceable computer systems, it becomes desirable to implement a computer chassis design that allows for easy access to the motherboard. Allowing for easy access to the motherboard makes it easier to access key electronic devices such as the processor and system memory so that, for example, a computer system user can quickly upgrade either of these components. Unfortunately, because the chassis design of the prior art structure of FIG. 1A affixes motherboard 11 to the bottom of chassis 15 using screws 10, it is necessary to remove the PCBs and other electronic devices that may be placed above motherboard 11 inside the chassis before removing the screws. This makes it difficult to access and service the electronic components on the motherboard.